The diameter of a cylindrical box of cds is 5 inches. the height of the box is 4 inches. whuch measurement is closest to the total surface area of the cd box in square inches

The equation for the surface area of cylinder is , where SA = surface area, r = radius, and h = height.

To help you remember this equation, remember that the surface area is the total area of all the surfaces of a shape. A cylinder is made up of two circles and a long rectangle that creates the body of the cylinder (see picture). The surface area is thus the area of the two circles () plus the area of the rectangle (), which has a width of 2πr (aka the circumference of a circle) and a height of h. 

Back to the problem:
You are told that the diameter of the cylinder is 5in. Remember that the diameter = 2r (2 times the radius). That means the radius, r = 5/2 = 2.5 in. You are also told the height, h = 4in. Plug these values into the equation for the surface area of a cylinder:


The surface area is about 102.1 square inches.